In recent years, with the rapid development of the society, a photoelectronic-related component and equipment have remarkably been progressed. Among other things, a display which represents an image has spread wide for use not only in a television set, but also in a monitor device for a computer and information terminal device. While in such spreading, a requirement for a larger size and a smaller thickness of the display, or for a smaller size and a lighter weight thereof for the purpose of a portable application is ever increasing in the market.
When an effort to increase the size of the display and, for the purpose of the portable application, downsize thereof is made, a safety problem comes up.
A viewing surface of the display is ordinarily made of a glass plate. As a surface area of the glass plate becomes larger, the glass plate becomes more liable to be subjected to external impact and, then, broken. Further, as an opportunity of taking the display out for carrying it outside is increased more, an opportunity for the display to be subjected to the external impact is increased more and the display becomes liable to be broken.
The safety for the display against the external impact is controlled, as described below, by Japan Electrical Appliance and Material Control Law.
For example, in regard to protection for a cathode-ray tube, an appliance provided with the cathode-ray tube in which a nominal size of a diameter of a maximum portion (in a case of a rectangular shape, length of a diagonal line) is more than 160 mm is controlled as follows: in a state in which the cathode-ray tube is appropriately fitted on a cabinet, when a steel ball having a diameter of 50 mm and a weight of 500 g is dropped from a height of 1,400 mm on a front surface of the cathode-ray tube in a manner of a swinging pendulum, the cathode-ray tube is required to comply with the following standards: (1) when a protective plate is made of bonded glass or a synthetic resin, fragments thereof will not be scattered in front; (2) when the protective plate is made of tempered glass, any abnormalities such as a crack, breakage and the like will not be generated; and (3) when the cathode-ray tube is not provided with the protective plate, fragments thereof will not be scattered in front.
In regard to mechanical strength of the cathode-ray tube, in an appliance provided with the cathode-ray tube in which a nominal size of a diameter of a largest portion (in case of a rectangular shape, a diagonal line length) is more than 160 mm, when the cathode-ray tube (in case of having a protective plate, inclusive of the protective plate) is broken by a mechanical method or a thermal shock method, weight of fragments of broken glass scattered in a space provided between barriers which are placed at a distance of 900 mm and at a distance of 1,500 mm respectively in front of the cathode-ray tube is 15 g or less for a single piece and 45 g or less for total fragments and, further, any piece having a weight of more than 1 g will not fly over the barrier placed at a distance of 1,500 mm in front of the cathode-ray tube.
A more specific method of application of mechanical strength can be found, for example, in UL (Underwriters Laboratories Inc.) specifications. Take, for example, a case of drop test. In this test, a display element is dropped on a plate from a height of 750 mm. The plate is made of hardwood and has a thickness of 20 mm. Two plates each having a thickness of 20 mm are folded with each other and, then, the resultant laminated plate is placed on concrete and, thereafter, the plate is placed on the laminated plate.
As a display which can realize an enlargement of a size and also decrease in thickness, in addition to a conventional liquid crystal display (LCD), a plasma display panel (PDP) has recently attracted people's attention and is expected to be a large-sized display of the next generation.
As for the PDP, an optical filter is ordinarily provided on a viewing surface thereof. This optical filter is used for the purpose of shielding an electromagnetic wave and a near-infrared ray emitted from a PDP main body. Further, there are may cases in which the optical filter concurrently has a function to change a luminescent color into that having a favorable color tone.
The optical filter is prepared by imparting a transparent support which comprises a glass plate or a resin plate with a function. Since, in a conventional PDP, a transparent supporting substrate of the optical filter has a function as a front protective plate, the conventional PDP can easily attain safety standards defined by Japan Electrical Appliance and Material Control Law.
However, it is necessary to substantially decrease a production cost in order to allow the PDP to be popularized in the market. A cost reduction of the optical filter thereof is also required whereupon a material cost and a production cost by a sheet-feeding method of the transparent supporting substrate are items to be reviewed.
On the other hand, in the liquid crystal display (LCD), the viewing surface thereof is ordinarily provided with a polarizing plate, a phase difference plate, a film having an anti-reflection function and the like. Since these articles substantially have a function of protecting the display, the conventional LCD easily attains safety standards defined by Japan Electrical Appliance and Material Control Law.
Ordinarily the size of the screen of the LCD is up to 20 inches, but, since there is a rapidly expanding requirement in the market for a larger display, an effort for further enlargement of the LCD has been made. However, as the size of glass which becomes a substrate is larger, the glass is more liable to be broken whereupon it is difficult for a display having such a larger size of glass to satisfy the safety standards defined by Japan Electrical Appliance and Material Control Law by a conventional technique.
The LCD for the application of a small-sized portable terminal is expected to be frequently carried around whereupon there are many opportunities in which the LCD receives external impact, for example, by being dropped, hit or the like. In such opportunities, although the LCD has resistance against impact to a certain extent by the help of protective functions which are possessed by the polarizing plate and an anti-reflection-functional film provided on the viewing surface, such resistance is not sufficient. In fact, a majority of complaints which portable terminal manufacturers receive from portable terminal users are attributable to a phenomenon that the LCD is broken.
Also in regard to an organic EL display (OELD) and a field emission display (FED), as the sizes thereof become larger, glass substrates thereof are more liable to be broken in the same manner as in the LCD whereupon it also becomes difficult for these displays to comply with the safety standards defined by Japan Electrical Appliance and Material Control Law. Also for the application of the small-sized portable terminal, damage and breakage to be caused by the impact become a problem. Particularly in cases of OELD and FED, since these displays have neither the polarizing plate nor the phase difference plate which the LCD has, that is, have a smaller number of substantial protective members than the LCD whereupon these displays are more liable to be broken than the LCD.
It is an object of the invention to provide a laminate which can easily attain safety standards for, e.g., impact resistance and the like, for example, when the laminate is provided on a viewing surface of a display while aiming for a cost reduction, and a display apparatus using the laminate.